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 ###Instrução: Qual é o 1991 para 2R 1999?
 ###Tabelas: CREATE TABLE college_career_statistics (college_career_statistics_id AUTO_INCREMENT PRIMARY KEY, Season VARCHAR, GP/MP VARCHAR, Kills INT, K/Game INT, Errors INT, Total Attempts INT, Percentage INT, Assists INT, Service Aces INT, Digs INT, Solo Blocks INT, Block Assists INT, Total Blocks INT, Points INT) CREATE TABLE nfl_championships (nfl_championships_id AUTO_INCREMENT PRIMARY KEY, Game VARCHAR, Date VARCHAR, Referee VARCHAR, Umpire VARCHAR, Head Linesman VARCHAR, Line Judge VARCHAR, Field Judge VARCHAR, Back Judge VARCHAR) CREATE TABLE grand_slam_singles_performance_timeline (grand_slam_singles_performance_timeline_id AUTO_INCREMENT PRIMARY KEY, Tournament VARCHAR, 1988 VARCHAR, 1990 VARCHAR, 1991 VARCHAR, 1992 VARCHAR, 1993 VARCHAR, 1995 VARCHAR, 1996 VARCHAR, 1997 VARCHAR, 1998 VARCHAR, 1999 VARCHAR, 2000 VARCHAR, 2001 VARCHAR, Career SR VARCHAR, Career Win-Loss VARCHAR) CREATE TABLE 2007_2008_table (2007_2008_table_id AUTO_INCREMENT PRIMARY KEY, Club VARCHAR, Played VARCHAR, Won VARCHAR, Drawn VARCHAR, Lost VARCHAR, Points for VARCHAR, Points against VARCHAR, Tries for VARCHAR, Tries against VARCHAR, Try bonus VARCHAR, Losing bonus VARCHAR, Points VARCHAR) CREATE TABLE mps_1832–1885 (mps_1832–1885_id AUTO_INCREMENT PRIMARY KEY, Election VARCHAR, 1st Member VARCHAR, 1st Party VARCHAR, 2nd Member VARCHAR, 2nd Party VARCHAR)  
SELECT 1991 FROM grand_slam_singles_performance_timeline WHERE 1999 = 2r